Multiple step continuous contacting of immiscible substances



March 21, 1961 w. A. VAUGHN MULTIPLE STEP CONTINUOUS CONTACTING OF IMMISCIBLE SUBSTANCES Filed May 31, 195'? INVENTOR.

WlLLIAM A. VAUGHN @MM/.f o.

GENT.

MULTIPLE STEP CONTINUOUS CONTACTING OF IMMISCIBLE SUBSTAN CES William A. Vaughn, St. Albans, W. Va., assignor to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware Filed May 31, 1957,`Ser. No. 662,732

3 Claims. (Cl. 260-461) The present invention relates to a method for multiple contacting of a substance continuously with immiscible substances diiering in composition but miscible with each other.

In the chemical processing industry several steps frequently have to be performed in a particular order. Examples comprise removal. of an impurity which interferes with a subsequent operation, reduction of acidity for subsequent operation in which free acid would be objectionable and reduction of .alkalinity kfor subsequent processing in which alkali would be objectionable. Whether it is desired to remove something from or to add something to a composition, the composition must be brought into adequate intimate contact with the reagents. The present invention relates to situations Where the substance; to be contacted is immiscible with the treating substances.

The invention is particularly applicable to washing of liquid organic chemicals to remove by-products. When successive washes diifering in composition are required, batchwise Washing is a simple operation and a requirement for dilcrent washes and a particularorder of contacting introduces no problems. T o accomplish the same result continuously is much more diicult. The present invention combines a multiple step washing operation into a single continuous process.

In accordance with Ythe present invention, ra method for multiple contacting of a substance continuously with immiscible substances diifering in composition but miscible with each other is provided which comprises continuously feeding the composition to becontact .treated into a mixing zone and passing it counter-currently through successive regions of contact, oney immiscible substance being introduced at a point remote from 'the feed point and a second immiscible substance. mis'cible with the -rst being introduced-at an intermediatepoint and withdrawing continuously the combined treatingsubstances and treated product.

The accompanying drawing illustrates an apparatus and system eminently suitable for carrying out the principles of the invention, although this is only illustrative. The material to be treated is pumped from the container 6 into the top of Van extraction column 1 through line 2. The column contains nine wire mesh coalescing sections 3 separated by eight mixing sections 4, each of which is agitated by the stirrer 5. The extraction colum is of glass 6 feet high and 3 inches inside diameter. The coalescing sections are inches high separated by 11/2 inch mixing sections. The agitator is a series of four-bladed turbines on a single shaft driven by an air motor. Each turbine is 1% inches in diameter and inch thick. One of the materials to be contacted is fed from container 7 through a preheater of steam-jacketed pipe S and a rotarneter 9 into the bottomof thecolumn through line 10. The second treating substance isffed from container 11 through rotameter 1'2 into the middle of the column through line 13. The treated material is continuously removed from the bottom of the column Vthe dimensions of the column and agitator may be varied Vas may the composition of the packing.

In one specific embodiment of the invention, the material to be treated is a slurry of inorganic salts and a heavy organic liquid constituting about 60 percent of the total weight. Besides Y the large amount of salts to be removed, the organic liquid also Vcontains 1 to 2 percent of a phenolic compound which-has to be reduced to 0.1 percent or less. The phenol can be removed by washing with soda ash solution to formY the sodium phenate and then water washing to remove'the Vsodium phenate. It is necessary to remove the `saltsbefore contacting the vorganic liquid with soda ash Ybecause sodium bicarbonate, one of the salts in the crude slurry, buffers the system at such a 10W pH that the sodium phenate cannot be formed. Therefore, three separate operations are needed: A Wash to remove theV inorganic salts, a soda ash wash to form the sodium phenate, and a water wash to remove the sodium phenate.

The three-step Washing is accomplished in the extraction column described. In the upper section of the colum the lcrude product is contacted with wash Iwater to remove the solid salts. Thecombined washes from feed tanks 7 and 11 rising through the upper section of the column Contact the descending organic liquid thereby removing Water-soluble salts. f The organic liquid then passes into the center section where dilute soda ash solution from tank 11 feeding into the middle of column through line 13 converts the phenol to sodium phenate. In the lower half of the column, fresh Water from tank 7 feeding into the bottom of the column through line 1t) extracts the sodium phenate, and the washed organic liquid is removed fromV the bottom through line .14. The

' water leaving the column contains sodium phenate, Vexcess soda ash and inorganic salts. Y

,'To start the operation, hot water is fed for several minutes to heat the column. When the efiiuent Water is warm, .the water flow is reduced to the required rate and soda ash solution-fed -to build up the soda Vash Aconcentration inthe upper portion of the column. When .runs the organic liquid isO-p-nitrophenyl 0,0-dimethyl- .phosphorothioate, the phenol impurity being'p-nitrophenol. ln the remaining runs the organic liquid is Op nitrophenyl- 0,0diethylphosphorothioate, the phenol im- ,purity again being vp-m'trophenol. reported in lbs./.hr.'/ft.2 as well as in lbs/hr. in order Vto provide data directly applicable toany size equip-Q ment.` The data in the section of the analysis Vlabelefc'l 5 f Rewashed refers to values after washingy the' processed product ii with water -in a separatory funnelY until the g The feed rates f are phenol content is constant. This gives the portion of the total phenol content insoluble in water. The portion of the total phenol removed by rewashing in a separatory funnel ispresent as the water-soluble sodium phenate. This value, obtained by the difference of the total phenol and free phenol, is reported as sodium phenate.

as to maintain in the column a wash solution containing 35% caustic soda. The brine fed into the column may vary from 25% to saturated sodium chloride solution. Preferably, the process is conducted at room temperature.

It is intended to cover all changes and modifications of the examples of the invention herein chosen for pur- Table l Run No 1 2 3 4 5 6 7 8 9 10 11 12 Water Rate lbs./h 120 150 60 120 90 120 120 150 100 100 120 1bs./hr./it.2 2, 450 3, 060 1, 225 2, 450 1, 835 2, 450 1, 630 2, 450 3, 060 2, 040 2, 040 2, 450 Crude Slurry Rate:

. 30 30 15 30 20 34 30 28 40 30 33 20 lbs./hr./ft.2 613 613 306 613 613 700 408 570 805 618 680 507 Soda Ash Rate, 100% Basis:

lbs. r 1. 1. 15 0.26 0.50 0.40 0.60 0.35 0. 50 0.67 0. 44 0. 43 0.43 23.6 23.6 5. 4 10. 2 8. l 12. 3 7. 2 10. 2 13. 4 9. 0 8. 9 8. 9

65 60 80 75 76 77 78 77 75 76 77 76 Out, C 56 60 60 59 agitation, r.p.m 406 511 420 406 427 434 434 455 497 305 395 Analysis: e

Total Phenol, Percent in Feed 0.85 0. 85 0. 85 0.85 1. 06 1. 25 1. 25 1. 25 1. 25 1. 95 2.05 1. 71 Total Phenol, Percent; alter Processing- 0. 14 O. 11 0. 05 0.09 0. 31 0. 42 nil nil nil 0.03 0. 05 0.05 Rewashed* l Free phenol, percent 0.06 0.1 1 0. 12 0.12 Sodium phenate, percent 0. 08 m1 0. 19 0.30

Column Hooded.

Comparing runs 1 and 2 with 3 and 4, the limiting variable s temperature. In this particular operation a minimum of 75 C. inlet water temperature is required for efficient operation. It is then a simple matter to adjust the How rates to achieve complete rapid removal of impurities continuously.

The form of the total phenol shows which portion of the column is limiting under the operation conditions used. For example, in run No. 2 the total phenol content and the free phenol content are the same. This shows that the water wash section performed its function perfectly because all the sodium phenate was removed. However, the soda ash section did not convert all the free phenol to sodium phenate. As indicated, this was corrected by increasing the water temperature at the inlet. In run No. 6 the total phenol content is much larger than the free phenol content, indicating that the water wash zone of the column was limiting since all the sodium phenate formed in the soda ash section was not Washed out in the water wash zone. Moreover, the etliciency of the soda ash zone is low because the free phenol content is higher than the maximum allowable. The operation is corrected by lowering the ratio of the crude slurry to Water and increasing the ratio `of soda ash to crude slurry.

In another specic embodiment of the invention the material to be processed is a solution in toluene of 2-(2- cyanoethoxy)ethylacrylate containing acrylic acid, toluene sulfonic acid and other impurities. It is necessary to treat the product with brine to reduce solubility of the monomer and to neutralize the free acidity. It is then necessary to remove the excess base. Therefore, two separate operations are needed: A wash to reduce solubility of the monomer and neutralize free acidity and a wash to remove excess base.

The objects are accomplished in the extraction column described but the organic solution containing a small amount of toluene sulfonic acid in suspension is lighter than water and is pumped into the bottom of the column where it rises countercurrently through the washing stages. Caustic soda solution is fed into the middle of the column and 25 brine into the top of the column. The rising organic liquid tirst contacts a mixture of the brine and caustic which neutralizes the free acidity. The brine prevents excessive loss of product by diminishing solubility in the aqueous phase. The excess caustic is then removed in the upper half of the column. The ow of caustic is preferably adjusted so poses of disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. A method of washing an organic liquid ester containing as impurities organic acid in solution and inorganic salt in suspension whickcomprises continuously feeding the material to be e acted into a mixing zone into contact with combined aqueous washes of different treating agents, passing it countercurrently through successive stages of contact without separating layers, fresh Water being introduced continuously near the opposite end of the mixing zone and aqueous alkaline solution being introduced continuously at an intermediate point.

2. A method of washing O-p-nitrophenyl di(lower alkyl)phosphorothioate containing inorganic salts including sodium bicarbonate in suspension and p-nitrophenol in solution which comprises continuously feeding the material to be extracted near the top of a mixing zone into contact with combined aqueous washes of different treating agents and passing it countercurrently through successive stages of contact, fresh Water being introduced continuously near the bottom of the mixing zone and aqueous soda ash solution at an intermediate point, the temperature of the water at the inlet being maintained at a minimum of 75 C.

3. A method of washing an organic liquid acrylic acid ester partially soluble in water with aqueous washes of different treating agents which ester is lighter than the Washes and contains acrylic acid impurities which comprises continuously feeding the ester to be treated near the bottom of a mixing zone into contact with combined aqueous washes of diterent treating agents and passing it countercurrently through successive stages of contact, aqueous concentrated brine being introduced near the top of the mixing zone and an aqueous solution of base being introduced near the midpoint of the mixing zone.

References Cited in the file of this patent UNTTED STATES PATENTS 

2. A METHOD OF WASHING O-P-MITRIPHENYL DI(LOWER ALKYL) PHOSPHOROTHIOATE CONTAINING INORGANIC SALTS INCLUDING SODIUM BICARBONATE IN SUSPENSION AND P-NITROPHENOL IN SOLUTION WHICH COMPRISES CONTINUOUSLY FEEDING THE MATERIAL TO BE EXTRACTED NEAR THE TOP OF A MIXING ZONE INTO CONTACT WITH COMBINED AQUEOUS WASHES OF DIFFERENT TREATING AGENTS AND PASSING IT COUNTERCURRENTLY THROUGH SUCCESSIVE STAGES OF CONDUCT, FRESH WATER BEING INTRODUCED CONTINUOUSLY NEAR THE BOTTOM OF THE MIXING ZONE AND AQUEOUS SODA ASH SOLUTION AT AN INTERMEDIATE POINT, THE TEMPERATURE OF THE WATER AT THE INLET BEING MAINTAINED AT A MINIMUM OF 75* C. 